A digital stereophotogrammetric method capable of providing quantitative measurements from stereophotographs of the optic nerve head has been developed and employed in our laboratory to study the optic cup. The major thrust of the investigation has been in evaluating the reproducibility of the technique, and it has been shown that the best results occur utilizing stereophotographs taken simultaneously through the Donaldson fundus camera. It was determined that the shallower cups encountered larger percentage errors than the deeper ones, and that substantial improvements in parameter reproducibility were obtained when finer sampling intervals were used during film digitatization. In addition, a study comparing reproducibility of cup depth, width, cup cross sectional area and cup volume as determined by the digital photogrammetric procedure with those values obtained from analog photogrammetry and manual analysis revealed generally superior reproducibility of the digital photogrammetric analysis. Patients with elevated intraocular pressure will be followed in order to find if the method is a more delicate test in determining early cupping than clinical observation. The possibility of reversing early cupping and field loss by therapy will be explored. In addition, the relationship between the quantitative measurements of the optic nerve head cupping and visual field loss will be examined.